Management prefer lean manufacturing to optimize cost & increase efficiency but many fail to achieve. What could be the reasons?

"Without Standardisation, there can be no Kaizen" - Taichi Ohno.

Improvements need to be sustained through good discipline & adherence to process.  This requires a change in the organization's culture.  Otherwise, the lean efforts would results in good ideas & good solutions, but poor implementation.  Yet, sustained implementation is the one that gives the fruits & determines the success.

Paying more attention to outcome and "Quick Wins" than Building Continuous Improvement Culture 

Examples: Starting by reducing downtime and ignoring profound work on5S, Visual Management and Team Building

Lean manufacturing couldn't be implemented properly if doesn't involve top management into low management in the organization. The most important thing is the organization has to improves their human resources to achieve low cost and high efficiency. 

-not enough patience because transfering to lean management could cost at first but later on it would generate the required profits,or the need for "GEMBA" which is to go see for yourself in the factory floor and not only through documents to find out the real problem from the people most involved in the operation

The basic understanding of LEAN is missing and on the top - you require a true leader who can bridge the various parties and can amke them work hand on hand. There is no magic but a matured team work.

The reason behind that would be that we are not taking the principle of lean, but follow the books while some times following blindly the books while don't asses our resources and what the level in lean we are seeking for.

Without a simplification anything can't be done. 

Most of the managers start to be Lean as a "project". However Lean is not a project. Because each project starts and ends. In fact, Lean is an endless way, it is continious improvement.

On the other hand some of managers can not start Lean Transformation in whole organization. They start with the understanding of "Pilot Project", it is an end of Lean! Lean can not be a partly implementation. It is a transformation of culture.

What is more, mostly the middle-level-managers affraid from Lean and they resist. Because they feel their importance will be finish or the organization will not ask his/her capabilities anymore after development and sharing/teaching competencies.

Lean is a whole transformation. This is why HR is the key department for a LeanTransformation. I always start from HR contrariwise manufacturing!